Although a 3.5-to-1 cholesterol ratio is optimal, the American Heart Association says a ratio of 5-to-1 is acceptable, reports the Mayo Clinic. Cholesterol ratio is one of the tools used to determine if a person has an increased risk of developing heart disease. Low cholesterol ratios are associated with a lower risk of heart disease, while a high cholesterol ratio is linked with an increased risk of heart disease. Cholesterol ratio is determined by dividing the total cholesterol level by the HDL level.